Hyperthyroidism in pregnancy is associated with increased foetal and maternal morbidity. Hyperthyroidism occurs in 0.20.6% of pregnancies. This suggests that based on 23,000 deliveries in the 3 major Dublin maternity hospitals that 4060 cases per year would be expected to be at risk of a poor outcome from hyperthyroidism.
To clarify those factors associated with poor outcome in hyperthyroidism in pregnancy we undertook an audit of 53 cases of hyperthyroidism in pregnancy attending from 20042005. Women with hyperthyroxinaemia secondary to hyperemesis were excluded. Demographic data, maternal thyroid function tests, doses of anti-thyroid medications were noted. Pregnancy outcomes, birth weight and neonatal TFTs were noted. Cases were divided according to those Delivering pre 37 weeks (Group A, n=11) and at term, post 37 weeks (Group B, n=42).
Results: Mean age was 31±5 years. Mean booking to OPD at 13±5 weeks gestation. Mean delivery gestation was 39±1 weeks in-group A, 35±3 weeks in group B (P<00.1). Mean birth weight 3.3±0.7 kg. One neonatal death occurred in-group A.
In Group A, baseline TSH was 0.09±0.1, P<0.05 vs Group B (1.1±1.3). By end of the second trimester, TSH in Group A was 0.17±0.2, P<0.05 vs Group B (0.88±1.0). By end of third trimester TSH was 0.34±0.5 (GROUPA), P<0.05 vs. Group (0.98±0.9). Average BW in Group A was 2.5±0.9 kg, P<0.01 vs Group B (3.44±0.6 kg)
Conclusion: TSH levels were significantly lower in those women with pre-term delivery. This suggests that sub-optimal control of hyperthyroidism during pregnancy is associated with increased infant morbidity or mortality